Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Goes well beyond the annotations: the invoice number is system-generated, totals and VAT are computed from rows, the entry is booked to the ledger immediately (not a draft), it fails on a locked period, it cannot be edited or deleted through this server, the server never retries, and rate limits of 60/min and 1000/24h are stated.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Purpose and create-semantics are front-loaded in the first two sentences, with prerequisites, return values, and rate limits following in logical order. It runs long (nine sentences) but nearly every sentence carries actionable information.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description compensates by naming the return values (invoiceId, number, totals). It covers the destructive, non-idempotent, non-editable nature of the call and all prerequisite list tools, leaving nothing essential unsaid for a 9-parameter mutation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema itself documents every field including nested rows. The description adds only the source-of-truth hints (article codes, VAT codes, client existence), which largely duplicate the schema's own descriptions, so the baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Post a new sales (client) invoice') plus the underlying API endpoint, which distinguishes it from sibling creators like create_ledger_entry and create_payment. An agent can identify it as the sales-invoice creator without reading the schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives concrete preconditions: the client must exist (pointing at smartaccounts_list_clients), row codes must come from smartaccounts_list_articles, and vat_pc from smartaccounts_list_vat_rates. It also notes failure when the period is locked, but does not discuss when a payment or credit note would be the better call.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.